I installed thumbnailers:
sudo apt-get install ffmpeg ffmpegthumbnailer gstreamer0.10-ffmpeg(http://askubuntu.com/questions/2608/nautilus-video-thumbnails-without-totem)

Then I noticed, that in Wattos 8 /usr/share/thumbnailers folder is missing, so I copied it from Peppermint 5 installation.
After reboot thumbnails were working.

Included zipped thumbnailers folder from Peppermint 5

If you are using VirtualBox with Guest Additions, you must change uids for user vboxadd and group vboxf.

sudo usermod -u 998 vboxadd
sudo groupmod -g 998 vboxsf

If you dont do this, you can only login as guest in dist-mode ramastersys-iso.
Same changes are needed with new Peppermint 5 LXDE version.

EDIT: There was Fragadelics message about VirtualBox: IMPORTANT NOTE for Ubuntu if you have Virtual Box Guest Additions installed.
It was missing change of group uid, which was needed also (for me).